Almost every device in the kernel has a corresponding
``node'' entry in the /dev directory.
These nodes look like regular files, but are actually special
entries into the kernel which programs use to access the device.
The shell script /dev/MAKEDEV, which is
executed when you first install the operating system, creates
nearly all of the device nodes supported. However, it does not
create all of them, so when you add support for
a new device, it pays to make sure that the appropriate entries are
in this directory, and if not, add them. Here is a simple
example:

Suppose you add the IDE CD-ROM support to the kernel. The line
to add is:

device acd0

This means that you should look for some entries that start with
acd0 in the /dev
directory, possibly followed by a letter, such as
c, or preceded by the letter
r, which means a ``raw'' device. It
turns out that those files are not there, so you must change to the
/dev directory and type:

#sh MAKEDEV acd0

When this script finishes, you will find that there are now
acd0c and racd0c entries
in /dev so you know that it executed
correctly.

For sound cards, the following command creates the appropriate
entries:

#sh MAKEDEV snd0

Note: When creating device nodes for devices such as sound cards, if
other people have access to your machine, it may be desirable to
protect the devices from outside access by adding them to the
/etc/fbtab file. See fbtab(5) for more
information.

Follow this simple procedure for any other
non-GENERIC devices which do not have
entries.

Note: All SCSI controllers use the same set of
/dev entries, so you do not need to create
these. Also, network cards and SLIP/PPP pseudo-devices do not
have entries in /dev at all, so you do not
have to worry about these either.